Aesop's Fables: Townsend (1867)

THE BIRDS waged war with the Beasts, and each were by turns the conquerors.
A Bat, fearing the uncertain issues of the fight, always fought on the
side which he felt was the strongest. When peace was proclaimed, his deceitful
conduct was apparent to both combatants. Therefore being condemned by
each for his treachery, he was driven forth from the light of day, and
henceforth concealed himself in dark hiding-places, flying always alone
and at night.

George Fyler Townsend's translation of the fables, first published in 1867, is
in the public domain and can be found at many websites, including Project
Gutenberg.
Illustrations come from: Aesop's Fables, by George Fyler Townsend, with
illustrations by Harrison Weir, 1867, at Google
Books.